SLING-6258 - The PackageAdminClassLoader cannot load classes from bundles providing older API versions

* made sure to lock-down the bundle which provides first a resource / class from a requested package so
that subsequent calls for resolving classes / resources from the same package will always use the same
bundle

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1769127 13f79535-47bb-0310-9956-ffa450edef68